An electronic expansion valve is one of the important components composing a refrigerating system, and is one of the four essential components in a refrigerating system with the other three including an evaporator, a compressor, and a condenser. The working process of the electronic expansion valve generally includes: as a coil device is powered on or off, adjusting, by a valve needle, the opening degree of a valve port so as to regulate the flow of refrigerant.
In the prior art, the U.S. Pat. No. 5,735,501A discloses an electronic expansion valve, and reference may be made to FIG. 1 for details, which is a schematic structural view of an electronic expansion valve in the prior art.
As shown in FIG. 1, the electronic expansion valve in the prior art includes a valve seat assembly 1′ and a housing assembly 2′. A valve stem assembly 3′ and a valve port 1′1 are provided inside the valve seat assembly 1′. An electric motor 2′1 is provided inside the housing assembly 2′, and drives the valve stem assembly 3′ to move up and down along the axial direction via a gear system 2′2 so as to regulate the flow of fluid flowing through the valve port 1′1. However, the electronic expansion valve in the prior art has the following disadvantages.
In the above electronic expansion valve, the valve seat assembly 1′ is an integrated sleeve member, and is made of a tension member having a thin wall or a stainless steel tube. Due to the cylindrical shape of the side wall of the valve seat assembly 1′, the manufacturability in connection with a sight glass is poor, and due to a saddle surface existing at a connecting position of the side wall of the valve seat assembly 1′, an O-ring cannot be installed, which results in a poor sealing performance. Furthermore, due to the existence of the above saddle surface, a thread connection may be unsuited between the sight glass and the valve seat assembly 1′. If the thread connection must be adopted, the thickness of the wall of the cylindrical valve seat assembly 1′ has to be increased, which may cause an increased material consumption, an increased cost, as well as a cumbersome product. In summary, the electronic expansion valve in the prior art is not adapted to be mounted with a sight glass, and due to without the sight glass, it is impossible to know the situation of the fluid inside the electronic expansion valve timely, therefore causing a lot of inconvenience for the user in using the electronic expansion valve.
Furthermore, the Chinese Patent No. 200580023202.7 also discloses an electronic expansion valve. In this electronic expansion valve, as shown in FIG. 2, the valve seat assembly 22, due to its more complex structure, is formed by making a blank with a brass casting firstly, and then being shaped through lathe machining. First, due to the property of casting technique, in which some defects such as slag inclusion and blow hole may inevitably exist in the material, after the products are mounted and used outdoors for a period of time, it may generate verdigris under corrosion and the defective part is the weakest. The pressure in a refrigerating system is greatly higher than that outside of the valve, so that it is prone to leakage or fracture of the valve body due to insufficient strength, which may affect the service life and liability of the product and may result in failure of the function of the whole refrigerating set, causing huge losses to the freshness preserving products stored in a large cold storage, a supermarket cooler or a refrigerator plant. Second, since the fusion point of the brass is approximately more than 930 degree, when braze welding is performed in a tunnel furnace teemed with reducing agent protection gas, the welding temperature of the procedure must be lower than the fusion point of the brass, and accordingly, a welding material with high silver content has to be adopted in welding a connecting tube and the brass valve body, causing a hugely increased costs of the welding because of the rising of the silver price. Third, since brass casting is performed by a mould, if the customer has a different requirement, the mounting positions of the connecting tube and the valve seat need to be adjusted, and therefore a new casting mould needs to be made. However, it may take a long manufacturing period to make a new mould, thus resulting in an increased cost of production.
In view of this, a technical problem to be solved presently by those skilled in the art is to improve the electronic expansion valve in the prior art so as to enable the sight glass to be connected to the valve seat assembly conveniently.